Ms4a4a deficiency ameliorates plaque pathology in a mouse model of amyloid accumulation
Genome-wide association studies for Alzheimer disease (AD) risk have identified a number of genes enriched in microglia, including MS4A4A. Common variants in MS4A4A influence AD risk, MS4A4A expression, TREM2 signaling, and a specific microglial transcriptional state, though the exact role of MS4A4A in AD remains unclear. Using a mouse model of amyloid beta (A{beta}) accumulation (5xFAD), we examined the impact of Ms4a4a loss on A{beta} pathology. Before A{beta} accumulation, Ms4a4a loss reduces steady-state A{beta} levels and shortens A{beta} half-life in brain interstitial fluid. In aged 5xFAD Ms4a4a-deficient mice, plaques are more compact with reduced overall plaque burden. Microglia lacking Ms4a4a are more pro-inflammatory and produce more MMP-9, which may promote degradation of A{beta} and A{beta} fibrils. Human subjects that carry a variant near MS4A4A (rs1582763) that confers resilience to AD also exhibit significantly elevated levels of MMP-9 in their cerebrospinal fluid. Together, our results suggest that loss of Ms4a4a improves A{beta} pathology by altering A{beta} clearance, offering insights for therapeutic interventions in AD.